This invention relates to a trocar, and in particular to a trocar with a retractable point to reduce the risk of injuring internal organs during use.
An increasing number of abdominal surgical procedures are being performed with laparoscopic techniques in order to avoid a large skin incision. Typically in laparoscopic surgery, a special needle, similar to the pneumoneedle described in U.S. Pat. No. 4,808,168, is inserted through the skin, and used to inflate the abdominal cavity with CO.sub.2. Once the abdomen is adequately dilated, the needle is removed and a rigid access tube with a larger diameter (for example 10 or 11 mm) is passed through the skin in the same location. The tube provides access for the laparoscope, a small diameter cylindrical viewing device that allows the surgeon to see inside the abdomen. To drive the tube through the skin, the surgeon places a trocar in the lumen of the tube to provide a sharp leading cutting edge.
The trocar devices presently available, for example those shown in U.S. Pat. Nos. 4,535,773, 4,601,710, 4,654,030, 4,902,280, and No. 4,931,042, typically comprise a sharp point for penetrating the skin, surrounded by a spring-loaded protective sleeve. As these trocar devices are urged through the skin, friction with the skin causes the protective sleeve to slide proximally (rearwardly). After the access tube has penetrated through the skin, there is no longer friction between the protective sleeve and the skin, and the spring urges the protective sleeve distally (forwardly) to cover the sharp point, locking the protective sleeve in position to reduce the risk of accidental puncture of the underlying organs. These prior art trocars rely on a similar principle of operation: The friction or drag on the protective sleeve as the trocar is advanced through the skin pushes the protective sleeve back to expose the sharp point. Once the access tube has penetrated the skin, the drag on the protective sleeve is reduced and the sleeve accelerates distally (forwardly) under the bias of the spring to cover the point. A significant amount of force usually must be applied to penetrate the skin (particularly the tough facia), and it is often difficult for the surgeon to determine precisely when the skin has been penetrated, and therefore the trocar may continue to advance toward the underlying organs after it has penetrated the skin. Thus, the protective sleeve must "catch up" to the moving trocar point before the trocar reaches the underlying organs.
The trocar of the present invention provides a mechanism for retracting the trocar point upon penetration of the skin. Thus, the sharp trocar point begins to move away from the underlying organs upon penetration of the skin. Moreover, because of the proximal (rearward) motion of the point, the covering of the point is not dependent upon the sleeve "catching up" with the point as in the prior art trocars where only the sleeve moves. The trocar of the present invention can also provide a positive tactile signal, conveniently triggered by the retraction of the point, indicating when the trocar has penetrated the skin, so that the surgeon can stop advancing the trocar.
The trocar device of the present invention is of the type placed in the lumen of a cannula to facilitate inserting the cannula through the wall of a body cavity. The trocar generally comprises a point for piercing the wall of the body cavity, a protective sleeve mounted concentrically around the point for axial movement relative to the point, and means for biasing the protective sleeve distally (forwardly) relative to the point so that after the point penetrates the wall of the body cavity, the sleeve moves distally under the bias. The trocar of the present invention further comprises means for retracting the point relative to the protective sleeve after the point penetrates through the wall of the body cavity. The trocar device preferably also comprises means for triggering the retracting means upon the distal (forward) motion of the protective sleeve. In the preferred embodiment, the retraction of the point provides a positive tactile signal to the user that the skin has been penetrated.
Thus, the trocar of the present invention begins to retract the trocar point away from the underlying organs after the point penetrates through the skin, keeping the point further away from the organs. Furthermore, because of this retraction of the point, the point of the trocar of the present invention is covered more quickly than the point of a similar device that relies solely on the distal (forward) movement of a protective sleeve to cover the point. Finally, since the device can provide a positive signal to the surgeon when the skin has been penetrated, the surgeon knows when to stop advancement of the trocar. Thus, it is believed that the trocar of this invention reduces the risk of accidental organ puncture.
These and other features and advantages will be in part apparent, and in part pointed out hereinafter.